


Vivarium

by Not_You



Category: Harry Potter - J. K. Rowling, X-Men: First Class (2011) - Fandom
Genre: Alternate Universe - Fusion, M/M, Parseltongue, Snakes
Language: English
Status: Completed
Published: 2013-06-03
Updated: 2013-06-09
Packaged: 2017-12-13 20:16:51
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 6
Words: 4,277
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/828413
Author URL: https://archiveofourown.org/users/Not_You/pseuds/Not_You
Summary: <blockquote class="userstuff">
              <p>Trying to finally finish this, which was started ages ago for this kinkmeme prompt:</p><p> </p><p>  <i>Erik is the cute but grumpy guy who works at the local vivarium. Charles to come in weekly to ask Erik inane questions about reptiles in an attempt to get into his pants.</i></p><p> </p><p>  <i>Brownie points if Charles actually had a legitimate reason to be in the store the first time, maybe he teaches a science class that has a class pet turtle. </i></p><p> </p><p>I added the wrinkle of the Harry Potter universe so Erik could be a grumpy Parselmouth and Charles could teach Care of Magical Creatures.</p>
            </blockquote>





	1. Chapter 1

London's Herpetologic Fantastic Vivarium is a good place for someone like Erik. It's dark and quiet and the only people he ever needs to talk to are veterinary specialists and the occasional academic. While the schoolchildren come through he tucks himself into the supply closet and drinks cheap Patronus vodka out of a hipflask. The branding is in poor taste, but it probably is nasty enough to drive away dementors. The rest of the time he can go about his business and talk to his friends and not worry about anyone seeing the signs on his arm. There are a lot of different creatures here, and he can talk to any of them that don't have legs. He still feels for the ones that do, could make his way through his usual rounds blindfolded.

Today he's sitting on a rock by the largest pool, a spiral constrictor wound around his hands. She's very beautiful, in her crisp black and silver whorls, and he's telling her so, light and teasing as she spills herself through his grip and tells him that flatterers always come to a bad end, old and wise and conceited and utterly charming.

"That's just a serpent's aversion to the truth," he purrs, and it's his own fault for getting careless, really. For sitting here barefoot on this rock, like part of the display. Hell, his brand is even showing, Grindelwald's sign like a bruise on his skin just above the number. He has no idea anyone is there until a delighted voice says, "You're a Parselmouth!"

Erik nearly falls into the tank, looping his friend around his neck and scrambling back into his robe again, triangular glyph and 214782 hidden away. "What do you want?" He growls.

"Well, I came here to see about acquiring a tatzlwurm egg or two for a third-year class on magical creatures, but now I'm on a whole other tack." The sun of this little world makes it impossible for Erik to actually see the voice's owner, and it's starting to get to him. He carefully puts the snake onto a low branch and gets out of the enclosure as fast as he can without scrambling.

"I'm not actually part of the display," he snarls, feeling safer in the dark but still ridiculous as he slides back into his shoes.

"No, you're not. You'll have to forgive me, I'm a researcher at heart. Just sort of fell into teaching, really."

Ah. It's all clear now, the sweet young face, the earnest eyes, the ancient, tweedy robes. Old money gone with the war, fledglings hurled from high nests indeed. "I see." He doesn't take the boy's extended hand, but does lead him back to the office, and remembers to mention and apply the reduced rates for educators, though of course he's not carrying proof of his employment at Hogwarts and will have to come back next week. He spends the whole interview fucking around, and beams at the stupid plastic dinosaur Erik somehow never gets around to throwing away.

"Is this plastic? It's utterly charming, but you know they weren't really that color, with time-viewing being so much more refined now--"

"Muggles do what they can with what they have. Put it back where you found it." And he does, which is nice, but his blue eyes are full of too much sympathy.

"They do." He lines up the figure's little feet with their prints in the dust. "How brutal is the going rate on tatzlspawn?"

For two fertilized, which is surely what any Creatures master would want, the going rate is quite brutal; but relevant discounts make many wondrous things possible. He is elated, and manages to catch Erik's hand on the way out. He introduces himself as Charles Xavier, and startles Erik's own name out of him in a reflexive courtesy he had thought long gone. It's blessedly quiet after he leaves, but it's still a strange experience for Erik, and he turns it over on his way home.


	2. Chapter 2

There's nothing odd about it when Xavier shows up again, proper papers in hand. He picks through Erik's bookshelves while Erik goes over the forms, squinting through the reading glasses he has needed since the best repair job that could really be expected on a vicious blinding hex.

"There's a system," he says, not looking up.

"I could tell. I'm putting everything back where I find it. Not as if there's much room to do anything else, is there?" He drops to the floor and lets out a little cry of satisfaction. "In Defense of Salazar! I've been looking for someone else who's read this. Have you, or are you getting around to it? Oh, you have! …That's… really quite a lot of margin notes."

"I've had that book for years."

"So I see."

"Your forms." He tucks the glasses away again, and gets up, because the flametongues need their enclosure cleaned and it isn't happening with him sitting here.

"Thank you so much! And two weeks' preparation and shipping?"

"Exactly."

Xavier beams at him. "What would I do without you?"

"Lecture?"

The knowing and unoffended way Xavier laughs is kind of creepy and kind of comforting. "I suppose so." And he goes away for two peaceful weeks while Erik collects a new bite, comes to the rescue when some little shit launches his classmate's quill into the bandersnatch enclosure, and reads the Defense again, always amazed at Salazar Slytherin's foresight.

A knock at his door startles him and his wand is in his hand instantly. "I know I didn't make a proper appointment to bother you, but I really desperately need to know something."

Erik shudders, setting his wand down on the desk. "Yes?"

"Well, I've read up on all the requirements for a tatzlwurm nursery, but I've never actually raised them before and you don't have one here. Does it matter if the rocks are igneous or sedimentary?"

And so it begins, a barrage of inane questions and even more inane smalltalk. First just the tatzlwurms and his class, then the Defense and poaching and the despicable exotics trade, and whether the Ministry's reparations to muggles harmed in the war had been sufficient. After six months of regular visits, Erik realizes this is the most time he's spent with anyone he doesn't actually work with and who's not treating his battle fatigue, and Xavier has wormed a disquieting amount of information about him. His hometown doesn't really exist anymore, nor does his family, as a refugee in England his tuition to Hogwarts had been charity, and he has spent some time as an Auror.

A lot of people could intuit these, and a look at his forearm would tell the whole sad story, but Charles knows more. He knows that Erik's wand is ebony with the heartstring of a ferocious Hungarian Horntail at its core and that it is exactly nine inches long. That it's an Ollivander and had been one of the first things to even begin to make him feel better in his grief. Xavier knows how he takes his tea and which of the snakes are his best friends and how all he can understand from the Bandersnatch is when it swears. Shockingly enough, he does know when to shut up sometimes, like on February first when he just walks in (like he owns the place, that's been a feature since the beginning) and sets a plastic poppy on the desk. It's the most muggle token of remembrance he could have brought, and Erik cannot deny that he's touched.


	3. Chapter 3

"And what are you so happy about, Charles?" It's Easter Vacation, the school incredibly quiet as the golden afternoon sun pours in. His sister is helping him reorganize, which mostly means moving the clutter around.

"Because I have a date, Raven."

"You? Seriously?"

"You wound me, sister."

"Well, really. A date, not an appointment to get drinks and shag in an alley?"

"Dinner and rare fantastical reptiles."

"The Melmoth Exhibition?"

"It's not as if I can't afford it, and he likes reptiles." He flicks his wand, shifting a massive stack of books back to the shelf.

"...Oh Christ, the damaged goods at the vivarium?"

"I like him a lot, Raven."

"Did I say we weren't damaged goods? I can't believe tall, dark and snarly actually said yes, though."

"Only on several conditions." Charles laughs. "In fact, he wrote them down for me."

"Oh my god, give me that!" She snatches the tiny roll of parchment from his fingers and unfurls it. Erik's handwriting is beautiful and old-fashioned, with ornate, sinuous curves.

_1\. We will arrive early._  
_2\. If you're going to be ashamed of me if I speak Parseltongue, don't bother._  
_3\. If you mention my service in the war to anyone there you'll regret it._  
_4\. Baby is coming and that is not negotiable._  
_5\. If it must be the opening gala, you will not stand me up no matter what I wear._  
_6\. Regarding #5, for the love of god, don't wear tweed._

"Merlin's bollocks, brother. Who's Baby?"

"An orphaned blightfang he's hand-raising."

"You're out of your goddamn mind."

"I know, Raven. I know."

"Well, I can at least dress you for slaughter."

Erik's only dress robes have seen more funerals than anything else, high-necked and utterly unrelieved black. A look in the mirror tells him that he looks like Death himself, and he grimaces, casting about the room for some way to soften the effect and cursing himself for the time it takes, which is how he finds himself milling around with the rest of the crowd at the Apparition point, tense in his black and silver. It's mostly tweedy academics and the purest of purebloods and god he hates crowds. He's looking around again when a hand on his elbow makes him jump, ready to hex its owner into next week.

"Erik! Did you just arrive?"

"...Yes. Sorry."

"It's all right by me, you were the one who wanted to be early. You look amazing, by the way."

This can't help but mollify him somewhat, making meaningful the sacrifice of some of his few pieces of decent silverware now reduced nearly to foil, delicately picking out cuffs and hems and other edges, shimmering like starlight against the black. "…So do you." It comes out muted and reluctant, dragged between his teeth by truth. Charles beams up at him, eyes nearly glowing blue.

"Thank you! I have to admit that my sister dressed me, I'm hopeless on my own."

"I've seen the proof of that." He squeezes Charles's hand to soothe the sting, rewarded with a bright smile.

"So, where's Baby?"

"Darling little snakelet, your Uncle Charles wants to see you." It's a soft whisper, barely audible, but she hears, and pokes her tiny little neon red head up over his collar, flickering her tongue at Charles. He laughs and lets her go back to napping as Melmoth gives her introductory speech and they can at last wander through the exhibit. The place hums with magic, a temporary vivarium of the rarest magical species in the world, beasts almost never housed under the same roof. As much as Erik hates crowds and people in general, he can't hang on to a bad mood here, bathed in soft green light from some exhibits and moonlight from others, having strange and wonderful talks with some of the creatures. Charles enjoys watching him more than the exhibit.

There's even a blightfang, and Erik kneels down by its enclosure and lets Baby speak to it, adding his own soft and eerie hissing to the conversation. Sure enough, people move away from Erik, or give him frightened and disgusted looks, but Charles has seen it all before, when people find out about his legimancy. There's a talent no one trusts, and he just shifts around Erik, blocking his line of sight from the most obvious and hateful of them. The thought of anyone ruining this unprecedented good mood makes him want to growl.


	4. Chapter 4

They stay at the exhibit for a long time, Erik stopping to speak with almost every creature, talking in that soft, caressing hiss that makes Charles shiver. He kneels by low cages and leans on high ones, ignoring anyone and everyone who stares. There are fewer and fewer as the night goes on and more people leave. Erik is still talking to the Moonsnake when the closing of the vivarium for the night is announced. He looks up, surprised, and Charles smiles, taking his hand.

"Come on." He's glad that he had the foresight to make their dinner reservation quite late, since they're close to missing it as is.

"Thank you for bringing me here," Erik says softly as they make their way out, and Charles beams.

"I saw the notice in the Prophet and thought of you. Besides, I like listening to you speak Parseltongue."

"It disturbs most people."

"Come, Erik. Haven't you realized that I'm a lunatic?"

Erik grins down at him. "I guess so."

"I just hope you like Indian food."

"I like food, don't worry." Erik's eyes go remote for a moment. "I've been without often enough."

Charles squeezes his hand. "Well. Not tonight."

Erik smiles again. "No. Not tonight."

The restaurant is its dim, soothing self, and Charles can see Erik relaxing into it. Their table is tucked into a corner, a nice safe spot. Erik settles in and Baby sticks her tiny head out again, miniscule tongue flickering as she tastes the air. Charles smiles.

"She's utterly precious, Erik."

"Hear that, darling? You're precious," Erik coos, and Baby wriggles happily. Charles smiles at him, and when they order he gets a little bit of plain, steamed fish for Baby. Erik thanks him softly, and feeds Baby tiny chunks, both of them watching her little jaw unhinge as she swallows.

All of them eat well, and Charles is pleased to see Erik looking as content as a sleepy cat by the time they've finished with everything. He thinks again about what he has heard of the muggle leader Grindelwald worked with, and the conditions in the camps. He'll feed Erik fat if that's what it takes for him to know that he's safe now, that it's truly over. This place is more expensive than Charles used to have to worry about, but he and Raven still have savings enough that paying is no real hardship. As they walk back to the Apparition point, Erik takes Charles's hand without looking at him. Charles beams, and gently squeezes.

"…I don't suppose you'd like to come back to mine," Erik says, and Charles's heart does something like a drumroll. 

"Of course I would, Erik."

"I can't promise more than a drink."

"And you don't have to. I actually enjoy your company, Erik, or haven't you noticed?"

They vanish from a dingy alleyway behind the exhibition and reappear in a cleaner one on a muggle street. They're still in dress robes, of course, and Charles can't help but feel self-conscious as they walk along. Erik just chuckles. "Most of the neighbors are in bed by now. And they all think I'm some kind of Freemason, so robes are easy to explain."

"There's a brilliant dodge. My sister just tells people that I'm 'eccentric' in this pitying tone. She knows more about muggles, and makes fewer mistakes."

Erik smiles softly, eyes sad. He doesn't have to mention that he's muggleborn, parents killed by Hitler. Grindelwald had latched onto the madman's program and plucked muggleborn witches and wizards from those ranks of the damned, trying to train them to see their innate superiority. It generally hadn't worked, whole dead families a bit much to put aside. Charles squeezes Erik's hand again at the thought. Erik returns the pressure and then stops them, pulling out an ornate key to unlock the door of little red brick house with a tiny, neat yard full of abstract metal sculptures.

"How beautiful," Charles says, and Erik actually blushes, leading the way up the narrow steps and in. It's a dark, low little room, but comfortable. Erik flicks his wand to light the fire already laid in the fireplace, and switches on a few lamps, giving the place a cozy glow before he goes to an actual liquor cabinet.

"I keep the good stuff in here," he explains, reverently pulling out his one good bottle of firewhiskey, half gone now.

"I see," is all Charles says, watching Erik pour.


	5. Chapter 5

Erik supposes it was inevitable. Of course he was going to end up in bed with Charles, the only man fool enough to even try. They start out on the couch, a first kiss that burns with whiskey and a hesitant hand on his neck. He's just leaning into it when Baby asks what's going on, making him jump back. Charles blinks at him with those big, blue eyes.

"Erik? Are you all right?"

"I am. I just… Baby." He gestures to the collar of his robes, and hisses for Baby to please come out, because he's going to put her to bed. She complains a bit, but comes crawling out and lets him put her back in the terrarium she's living in. He pauses to adjust the spells to simulate night in her home country, and then goes back to Charles, irritated with himself for blushing. Charles smiles and reaches for him, pulling him down again and kissing him. Erik sighs and gathers Charles into his arms and then further into his lap, never breaking contact for more than a second at a time, breath mingling and teeth briefly clicking as Charles shifts. It has been a long time since Erik has held anyone like this, and he moans, clutching fistfuls of Charles's robe and nibbling at his lip and licking into his mouth. Charles shudders, and when they pause to catch their breath and gaze into each other's eyes, something happens. Charles is suddenly in Erik's mind, the presence caressing and sweet and wrong. Erik gasps and pulls away, shuddering.

"Charles, what—"

"I'm so sorry!" Charles is bright red, eyes huge. "My legimancy is usually under control!"

Erik stares for a long time, then sighs and gestures to the candlestick on the endtable, which has flowed into a slightly different shape with his arousal. "Like my metal magic?"

Charles looks, and smiles. "Yes, I suppose. Are you all right?"

"You didn't get into anything too painful, just don't do it again."

Charles nods, and kisses Erik again. It's more tentative this time, but soon they're mauling each other, Charles whimpering as Erik forces him onto his back and devours his mouth. "You do have a bed, don't you?" Charles gasps after they nearly fall off, and Erik nods, sitting up and scooping Charles into his arms again before standing and carrying him off to his bedroom. Charles whimpers and gazes up at him with dilated eyes. "Erik…"

Erik shudders, laying Charles out on top of the covers and ranging over him. "It's been a long time, Charles."

"That's okay." He tugs Erik down to kiss him again, sweet and slow. "We can take our time."

They do take their time, kissing each other until their lips are bruised and slightly numb before Charles rolls them over and starts working Erik's robes open, fingers gentle with the silver foil. Erik shivers, tipping his head back and gasping when Charles covers his bared throat in kisses. He basks in the attention like a snake on a rock, slithering out of his robes and hissing when Charles gently bites his chest. Charles chuckles. "You really are serpentine, aren't you, dear?"

"Mm. Then you're like a little blue-eyed kitten," Erik murmurs, and moans as Charles sucks one nipple, gently worrying it between his teeth. "Ohh, fuck..." Charles bites a little harder and Erik cries out, hips bucking. Charles grins at him and finishes unbuttoning his robes, sighing as he spreads them open. Erik squirms a little under his scrutiny and is glad to be wearing his one pair of black silk boxers.

"I just want to see you, Erik. We don't have to do anything."

"Hell with that," Erik mutters, and reaches up to peel Charles's robes off. Charles laughs and tries to help, and their hands tangle together. Erik growls and bites Charles's neck, rolling them over again and stripping him. Charles quivers and whines, rock hard, and Erik sighs, kissing him and then pulling away to get his wand out of his discarded clothes, casting a protective spell over both of them. Charles smiles up at him. 

"I'll take this as a good sign."

"You should," Erik says, finding his lube and slicking his cock, boxers kicked aside. Charles whimpers and wraps around Erik as they rock together, cocks trapped between them, thrusting and sliding.

"Erik," Charles gasps, "Erik, please fuck me."

Erik pushes one finger into Charles, shuddering at how easily Charles lets him in. "Please," Charles whimpers, and Erik groans, hiding his face in Charles's shoulder as he works another slick finger in, and then another, Charles begging for more. Erik shudders and pulls his fingers out, lining his cock up and sinking into Charles, staring into those wide blue eyes as he does.


	6. Chapter 6

Charles cries out over and over as Erik drives into him, gasping and clutching at his back. He seems to like it when Charles's nails dig in, so Charles makes sure to let them, not worried about cutting or bruising his partner when each one makes Erik grunt or groan, hips snapping forward in response and making Charles wail and cling even more tightly, legs locked around Erik.

"Yes, God, _Erik_ ," Charles gasps, "that's so good, so fucking good love, please…"

Erik grinds into him hard and deep, and Charles groans, eyes rolling back. His mouth is hanging open, and Erik's fingertips are suddenly there, two of them gently forcing their way into Charles's mouth. Charles whimpers and sucks them in, tongue swirling between them as he takes them deep into his mouth. Erik shudders and fucks Charles's mouth in time with his cock, nuzzling Charles's ear and… oh. _Oh_. That gentle, breathy hissing is Parseltongue. The realization is almost enough to make Charles come, and he groans and reaches for his cock, whining when Erik pulls out of his mouth and slaps his hand away. "Mine," he hisses, and Charles groans, crying out again as Erik squeezes his cock, stroking it rough and fast in time to his own last, jagged thrusts. They come at the same time, one sweaty, shuddering experience, and then just lie there and breathe together for a long time. Finally Erik eases off of and out of him, shifting to lie on his belly next to Charles. Charles sighs and stretches, then grimaces at the sight of Erik's back.

"Merlin's beard, I hope that doesn't hurt too much."

"Mm. Hurts just enough," Erik murmurs, but doesn't seem to mind when Charles starts kissing the welts.

"This one's bleeding," Charles says, and Erik shivers happily, moaning when Charles licks along the bloody line.

"Charles…"

"Mm?"

"Keep doing that." 

Charles is glad to obey, licking and laving each red welt and small cut as Erik moans and wriggles under him. "Keep this up and I'll want to fuck you," Charles murmurs, slowly getting hard again. Erik tenses, just a little, and then relaxes.

"Okay."

"You know we don't have to, Erik. You just have a really nice arse."

Erik chuckles and rolls over, not caring or not minding what it will do to the sheets. "And I want you," he says, and Charles does his best not to swallow his tongue. He kisses Erik and then rolls him onto his belly again, getting the lube. Erik groans and rises up on his knees, blushing at the low, hungry sound he makes as Charles just strokes Erik's hole, letting him get used to it. "You're doing so well, Erik," Charles murmurs, and then slides one finger in. It's a tight fit, but Erik groans and pushes back. Charles can feel that Erik isn't used to this, but that he would perhaps like to be. The thought makes him smile, and he carefully adds another finger. He takes his time with Erik, making sure that his fingers are sliding easily before adding more. Erik just rocks on his hand and groans deep in his chest for what feels like forever before panting that he's ready and for Charles to just fuck him already. Charles laughs breathlessly and ranges over him, carefully guiding his cock into Erik's tight heat. They both moan in the same helpless key, fitting together just as perfectly this way. Erik pants harshly into the pillow and then cries out as Charles sets up a deep, fast rhythm.

Neither of them lasts long, and they collapse together again, even more exhausted this time. "Haven't done that in a while," Charles chirps. Erik chuckles, fumbling for his wand and then cleaning the sheets with a charm. He sets his wand on the nightstand again and snuggles up to Charles from behind, curling around his back. Charles purrs and dozes off for a moment, waking up with a flinch at the feeling of something crawling over him. Erik's gentle, lulling hiss calms him down, though, and he realizes that it's Baby. She and Erik converse in quiet hisses, and Erik finally makes a very human noise of grumpy resignation. 

"Baby got cold, and insists on sleeping here tonight."

Charles smiles, turning in Erik's arms. "That's okay. I like snakes." He kisses Erik softly, and Erik melts, kissing back and holding Charles close.


End file.
